<?php

class InputFilter
{
    function process( $value )
    {
        // No need to filter really simple values
        if( ctype_alnum( $value ) )
        return $value;
        else
        return $this->RemoveXSS( $value );
    }

    /* RemoveXSS initially developped by kallahar - quickwired.com,
     * modified for TikiWiki Original code can be found here:
     * http://quickwired.com/smallprojects/php_xss_filter_function.php
     * Straightly borrowed from TikiWiki by the LimeSurvey project
     */
    function RemoveXSS($val) {
        static $ra_as_tag_only = NULL;
        static $ra_as_attribute = NULL;
        static $ra_as_content = NULL;
        static $ra_javascript = NULL;

        // now the only remaining whitespace attacks are \t, \n, and \r
        if ( $ra_as_tag_only == NULL ) {
            $ra_as_tag_only = array('style', 'script', 'embed', 'object', 'applet', 'meta', 'iframe', 'frame', 'frameset', 'ilayer', 'layer', 'bgsound', 'base', 'xml', 'import', 'link');
            $ra_as_attribute = array('onabort', 'onactivate', 'onafterprint', 'onafterupdate', 'onbeforeactivate', 'onbeforecopy', 'onbeforecut', 'onbeforedeactivate', 'onbeforeeditfocus', 'onbeforepaste', 'onbeforeprint', 'onbeforeunload', 'onbeforeupdate', 'onblur', 'onbounce', 'oncellchange', 'onchange', 'onclick', 'oncontextmenu', 'oncontrolselect', 'oncopy', 'oncut', 'ondataavailable', 'ondatasetchanged', 'ondatasetcomplete', 'ondblclick', 'ondeactivate', 'ondrag', 'ondragend', 'ondragenter', 'ondragleave', 'ondragover', 'ondragstart', 'ondrop', 'onerror', 'onerrorupdate', 'onfilterchange', 'onfinish', 'onfocus', 'onfocusin', 'onfocusout', 'onhelp', 'onkeydown', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture', 'onmousedown', 'onmouseenter', 'onmouseleave', 'onmousemove', 'onmouseout', 'onmouseover', 'onmouseup', 'onmousewheel', 'onmove', 'onmoveend', 'onmovestart', 'onpaste', 'onpropertychange', 'onreadystatechange', 'onreset', 'onresize', 'onresizeend', 'onresizestart', 'onrowenter', 'onrowexit', 'onrowsdelete', 'onrowsinserted', 'onscroll', 'onselect', 'onselectionchange', 'onselectstart', 'onstart', 'onstop', 'onsubmit', 'onunload','ondragdrop', 'dynsrc', 'lowsrc', 'codebase', 'xmlns');
            $ra_as_content = array('vbscript', 'expression', 'blink', 'mocha', 'livescript', 'url', 'alert');
            $ra_javascript = array('javascript');
            ///		$ra_style = array('style'); // Commented as it has been considered as a bit too aggressive
        }

        // keep replacing as long as the previous round replaced something
        while ( $this->RemoveXSSchars($val)
        || $this->RemoveXSSregexp($ra_as_tag_only, $val, '(\<|\[\\\\xC0\]\[\\\\xBC\])\??')
        || $this->RemoveXSSregexp($ra_as_attribute, $val)
        || $this->RemoveXSSregexp($ra_as_content, $val, '[\.\\\\+\*\?\[\^\]\$\(\)\{\}\=\!\<\|\:;\-\/`#"\']', '(?!\s*[a-z0-9])', true)
        || $this->RemoveXSSregexp($ra_javascript, $val, '', ':', true)
        ///		|| RemoveXSSregexp($ra_style, $val, '[^a-z0-9]', '=') // Commented as it has been considered as a bit too aggressive
        );

        return $val;
    }

    function RemoveXSSchars(&$val) {
        static $patterns = NULL;
        static $replacements = NULL;
        $val_before = $val;
        $found = true;

        if ( $patterns == NULL ) {
            $patterns = array();
            $replacements = array();

            // remove all non-printable characters. CR(0a) and LF(0b) and TAB(9) are
            // allowed this prevents some character re-spacing such as <java\0script>
            // note that you have to handle splits with \n, \r, and \t later since they
            // *are* allowed in some inputs
            $patterns[] = '/([\x00-\x08\x0b-\x0c\x0e-\x19])/';
            $replacements[] = '';

            // straight replacements, the user should never need these since they're
            // normal characters this prevents like
            // <IMG SRC=&#X40&#X61&#X76&#X61&#X73&#X63&#X72&#X69&#X70&#X74&#X3A&#X61&#X6C&#X65&#X72&#X74&#X28&#X27&#X58&#X53&#X53&#X27&#X29>
            // Calculate the search and replace patterns only once
            $search = 'abcdefghijklmnopqrstuvwxyz';
            $search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
            $search .= '1234567890!@#$%^&*()';
            $search .= '~`";:?+/={}[]-_|\'\\';
            for ($i = 0; $i < strlen($search); $i++) {
                // ;? matches the ;, which is optional
                // 0{0,8} matches any padded zeros,
                // which are optional and go up to 8 chars
                // &#x0040 @ search for the hex values
                $patterns[] = '/(&#[xX]0{0,8}'.dechex(ord($search[$i])).';?)/i';
                $replacements[] = $search[$i];
                // &#00064 @ 0{0,8} matches '0' zero to eight times
                // with a ;
                $patterns[] = '/(&#0{0,8}'.ord($search[$i]).';?)/';
                $replacements[] = $search[$i];
            }
        }
        $val = preg_replace($patterns, $replacements, $val);
        if ($val_before == $val) {
            // no replacements were made, so exit the loop
            $found = false;
        }
        return $found;
    }

    function RemoveXSSregexp(&$ra, &$val, $prefix = '', $suffix = '', $allow_spaces = false) {
        $val_before = $val;
        $found = true;
        $patterns = array();
        $replacements = array();

        $pattern_sep = '('
        .'&#[xX]0{0,8}[9ab];?'
        .'|&#0{0,8}(9|10|13);?'
        .'|(?ms)(\/\*.*?\*\/|\<\!\-\-.*?\-\-\>)'
        .'|(\<\!\[CDATA\[|\]\]\>)'
        .'|\\\\?'
        .( $allow_spaces ? '|\s' : '' )
        .')*';

        $pattern_start = '/';
        if ( $prefix != '' ) {
            $pattern_start .= '(' . $prefix . '\s*' . $pattern_sep . ')';
        }

        $pattern_end = '/i';
        if ( $suffix != '' ) {
            if ( $suffix == '=' || $suffix == ':' ) {
                $replacement_end = $suffix;
                $pattern_end = '(' . $pattern_sep . '\s*' . $suffix . ')' . $pattern_end;
            } else {
                $replacement_end = '';
                $pattern_end = $suffix . $pattern_end;
            }
        } else {
            $replacement_end = '';
        }

        for ($i = 0; $i < sizeof($ra); $i++) {
            $pattern = $pattern_start;
            for ($j = 0; $j < strlen($ra[$i]); $j++) {
                if ($j > 0) {
                    $pattern .= $pattern_sep;
                }
                $pattern .= $ra[$i][$j];
            }
            $pattern .= $pattern_end;
            $replacement = ( $prefix != '' ) ? '\\1' : '';
            // add in <> to nerf the tag
            $replacement .= substr($ra[$i], 0, 2).'<x>'.substr($ra[$i], 2);
            $patterns[] = $pattern;
            $replacements[] = $replacement.$replacement_end;
        }
        // filter out the hex tags
        $val = preg_replace($patterns, $replacements, $val);
        if ($val_before == $val) {
            // no replacements were made, so exit the loop
            $found = false;
        }

        return $found;
    }
}

?>
